Detection of anti‐type VII collagen IgE antibodies in epidermolysis bullosa acquisita

Summary Background Epidermolysis bullosa acquisita ( EBA ) is a rare pemphigoid disease involving autoantibodies to type VII collagen ( COL 7), a major structural component of anchoring fibrils. IgE autoantibodies to type XVII collagen ( BP 180) have been identified in bullous pemphigoid ( BP ), the prototype of pemphigoid diseases. Although the pathogenic relevance of IgG anti‐ COL 7 has been investigated, that of IgE in EBA remains unclear. Objectives To reveal the presence and pathogenic relevance of IgE anti‐ COL 7 in EBA . Methods We examined IgE antibodies in 109 patients with EBA by indirect immunofluorescence ( IIF ) and enzyme‐linked immunosorbent assay ( ELISA ). Results IIF with normal human skin revealed IgE reactivity in the basement membrane zone in 29 (26·6%) cases. To verify whether the IgE antibodies were specific to COL 7, we performed IIF with 21 clearly positive cases and the skin of a patient with dystrophic EBA , which does not involve COL 7. All cases showed negative results, indicating that IgE antibodies were specific to COL 7. In a modified IgG COL 7 ELISA for IgE, 16 (14·7%) cases were positive (three and 13 cases were negative and positive on IIF , respectively). We compared anti‐ COL 7 IgG and IgE, and found a weak but significant correlation ( r = 0·459, P < 0·001). EBA is clinically divided into a mechanobullous ( MB ; noninflammatory) type and an inflammatory ( INF ) type resembling BP . Of the IIF ‐positive cases, 11 of 30 (37%) had INF and nine of 48 (19%) had MB . Conclusions This study is the first to demonstrate the presence of circulating anti‐ COL 7 IgE in patients with EBA , which may correlate with the clinical phenotype.